Immunoglobulin G (IgG) Subclass Measurement (Serum)
This test measures the levels of different subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most common antibody and helps fight infections.
["IgG subclasses help identify immune system function and potential deficiencies."]
Key facts at a glance
- LOINC
- 107065-5
- Short code
- NKCD56
- Synonyms
- CD19-CD3-CD56+ (NK) NFr Spec FC
- Category
- chemistry
- Sample
- serum
- Container
- EDTA (lavender/purple-top) or ACD (yellow-top) anticoagulated tube for flow cytometry; sodium heparin tube also acceptable
- Units
- N/A
- Ref low
- 5
- Ref high
- 26
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- flow-cytometry
- CPT
- 86355
- SNOMED
- 399067008
- Specimen volume
- 3-5 mL of whole blood for adult samples; minimum 1 mL for pediatric samples; bone marrow aspirate: 1-2 mL in EDTA tube
- Stability
- Room temperature: 18-24 hours; refrigerated (2-8°C): up to 48 hours; do not freeze. Viability decreases significantly after 48 hours. Specimen should be kept at room temperature (20-25°C) and processed as soon as possible for accurate NK cell enumeration.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–48 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test to evaluate immune system function, diagnose conditions like immunodeficiency, or check for responses to treatments. It can also help identify why certain infections are recurring or persistent.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into a vein in your arm to draw blood. This is usually done in a clinic or hospital setting.
What the Results Mean
IgG subclasses are measured in arbitrary units per milliliter (U/mL) or milligrams per deciliter (mg/dL). Abnormal results may indicate immune system issues, such as low antibody levels or specific subclass deficiencies.
Common Conditions Linked to IgG Subclass Results
Low IgG subclass levels can be linked to conditions like common variable immunodeficiency (CVID), recurrent infections, or autoimmune diseases. High levels might suggest certain immune responses or chronic infections.
Reference range
CD19-CD3-CD56+ (NK) cells: 5-26% of total lymphocytes; absolute count: 100-480 cells/μL (varies by laboratory and age)N/A
No special preparation required. Recent corticosteroid therapy, chemotherapy, or immunosuppressive medications should be noted as they may affect NK cell counts. Specimen should be processed within 24-48 hours of collection for optimal viability.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
IgG Subclass Levels
Frequently asked questions
What does it mean if my IgG subclass test is abnormal?
How often should I get this test?
Can diet or supplements affect IgG subclass levels?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy